Electric battery packs are formed by a plurality of individual rechargeable battery cells connected in series. In general, each individual rechargeable cell comprises an electrically conductive casing which receives chemicals adapted to react to supply an electric current between an electrically conductive disc-shaped end wall, rigidly connected to one end of the casing, and an electrically conductive stud which is disposed at the other end of the casing and is electrically insulated therefrom.
A technique nowadays commercially used for producing such rechargeable battery packs comprises:
(a) connecting the battery cells electrically in series to form a preassembly; PA1 (b) wrapping an insulating sheath around the preassembly so as to insulate the electrically conductive casings from one another and ensure a mechanical connection between the various elements; and PA1 (c) placing the preassembly thus wrapped in a casing, such casing mainly performing a protective function and if necessary facilitating the establishment of electrical connections with the opposite end poles of the series arrangement of the cells.
However this technique has numerous disadvantages, including, for example, its complexity, which more particularly requires specialist personnel and results in long manufacturing times, a prohibitive cost for a large number of applications, and very mediocre reliability.
More particularly, the operation of winding or forming the insulating sheath around the preassembly of cells to insulate the casings, and ensure a mechanical connection thereof, can be long and complex when the cells have to be disposed in the form of parallel rows to obtain a compact battery pack.
Also, the commercial available rechargeable battery cells have wide tolerance variations, which correspondingly complicates the assembly processes.
In a modification of the above process, it has been proposed in U.S. Pat. No. 3,956,019 to weld electrical connecting plates to the output poles of a series arrangement of batteries, this welding being performed through openings in an end plate of the battery pack after the batteries and this end plate have been enveloped in a thermo-contractive synthetic resinous film. However, this still involves a rather complicated assembly procedure, not readily adaptable for automatic or semi-automatic assembly by machinery, and also relies on a film sheath to hold the battery pack together.